Kidney Week

Abstract: TH-PO794

Establishment of Diagnostic Criteria for Tubulointerstitial Nephritis with IgM-Positive Plasma Cells (IgMPC-TIN)

Session Information

• Pathology and Lab Medicine - I
  November 02, 2023 | Location: Exhibit Hall, Pennsylvania Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Pathology and Lab Medicine

• 1800 Pathology and Lab Medicine

Authors

• Takahashi, Naoki, Fukui Daigaku, Fukui, Fukui, Japan

Naoki Takahashi,

• Nishikawa, Yudai, Fukui Daigaku, Fukui, Fukui, Japan

Yudai Nishikawa,

• Watanabe, Yuki, Fukui Daigaku, Fukui, Fukui, Japan

Yuki Watanabe,

• Nishikawa, Sho, Fukui Daigaku, Fukui, Fukui, Japan

Sho Nishikawa,

• Nishimori, Kazuhisa, Fukui Daigaku, Fukui, Fukui, Japan

Kazuhisa Nishimori,

• Fukushima, Sachiko, Fukui Daigaku, Fukui, Fukui, Japan

Sachiko Fukushima,

• Kobayashi, Mamiko, Fukui Daigaku, Fukui, Fukui, Japan

Mamiko Kobayashi,

• Kimura, Hideki, Fukui Daigaku, Fukui, Fukui, Japan

Hideki Kimura,

• Kasuno, Kenji, Fukui Daigaku, Fukui, Fukui, Japan

Kenji Kasuno,

• Iwano, Masayuki, Fukui Daigaku, Fukui, Fukui, Japan

Masayuki Iwano,

Background

We proposed the IgMPC-TIN disease concept in 2017, and this disease concept is gradually gaining recognition in Japan. However, there are no clear diagnostic criteria for diagnosing IgMPC-TIN. We attempted to develop diagnostic criteria for IgMPC-TIN from both clinical and histological parameters or from only clinical parameters using cases collected from multiple institutions.

Methods

A total of 118 renal biopsy samples were collected from 61 patients with suspected IgMPC-TIN and 57 patients with other interstitial lesions from our hospital and national collaborating centers, and we performed double staining (IgM and CD138) using the immunoenzymatic method. Patients with M protein in their blood or urine and patients with diabetes mellitus were established as exclusion criteria. Then several nephrologists classified each case that did not meet the exclusion criteria from +3 (typical IgMPC-TIN) to −3 (not IgMPC-TIN at all). Based on 49 cases judged as +3 and 56 cases judged as −3, a decision tree-based diagnostic algorithm was created in JMP. Finally, the sensitivity and specificity of the diagnostic criteria created were calculated.

Results

In the diagnostic criteria consisting of histological and clinical parameters, the most important requirement was a maximum IgMPC infiltration count of ≥20/high magnification field of view (7400 µm²). The next most important requirement was the presence of urinary sugar, and the next requirement was the presence of primary biliary cholangitis (PBC). For diagnostic criteria consisting only of clinical parameters, the most important requirement was a serum IgM level of 267 or higher, followed by the presence of Fanconi syndrome. Sensitivity and specificity of each diagnostic criterion were 97.9 and 100% for histological and clinical parameters and only for clinical parameters. Although we consider diagnostic criteria that include histological parameters to be the gold standard, diagnostic criteria based solely on clinical parameters are also sufficiently accurate.

Conclusion

We analyze the clinical characteristics of IgMPC-TIN cases and develop criteria for the diagnosis of IgMPC-TIN based on histological and clinical parameters.

Funding

• Government Support – Non-U.S.